Metallized polymeric finishes can be used to complement and even replace bright, reflective metal surface treatments, particularly chrome plating. Polymeric structures having metallized finishes are commonly used as substitutes for articles, such as automobile grills, that are expected to have a chrome-plated appearance. Decorative polymeric components, in fact, are becoming standard in the automobile industry, primarily because plastics are relatively flexible, corrosion-resistant, and inexpensive. Plastic parts also reduce vehicle weight, which enhances performance, especially fuel economy.
Many patents disclose metallized substrates. For example, U.S. Pat. No. 5,035,940, for an Aluminum-Fluoropolymer Laminate describes a polymer-backed aluminum substrate with a weather-resistant polymer coating. Similarly, U.S. Pat. No. 5,536,539, for an Injection Molded Plastic Article with Integral Weatherable Pigmented Film Surface describes an automotive component formed from a molded polymer article having a decorative polymeric film surface. Both of these patents are commonly-assigned with the present invention.
As will be known by those familiar with the metallizing arts, chrome plating is perhaps the most common method of metallizing three-dimensional substrates, such as injection-molded substrates. Unfortunately, chrome plating not only carries onerous environmental concerns, but also introduces possible human health hazards.
A better method of metallizing polymeric substrates is to coat metal onto molded substrates, usually by vacuum deposition. In this regard, indium has gained acceptance as a preferred metal because on a microscopic scale it tends to form small, discrete deposits or “islands.” When bent or flexed, discontinuous metal layers tend to retain the desired optical properties better than do continuous metal films, which tend to fracture. Discrete metallization also minimizes electrical conductivity, which can hasten unwanted corrosion. For example, U.S. Pat. No. 4,431,711, for Vacuum Metallizing a Dielectric Substrate with Indium and Products Thereof addresses indium metallizing three-dimensional articles in a way that minimizes electrical conductivity and, consequently, corrosion.
In most cases, the metallized layer is covered with a transparent polymeric coating that physically and chemically protects its surface a so-called “clear coat.” Although in-situ metallization of formed polymeric articles is useful, it requires separate applications of a base coat, a metallized layer, and a clear coat. This necessitates drying time for each application, which lengthens the processing times (and hence costs) associated with metallizing three-dimensional articles. Therefore, depositing metal directly onto an article only after the article has been formed can be disadvantageous.
Alternatively, metallized film laminates (e.g., adhesive tapes) that can be applied to polymeric structures offer certain advantages over conventional in-situ metallization techniques. For example, metallized film laminates can be manufactured, stored, and shipped in roll form. Such laminates also facilitate customized application, limited only by adhesive effectiveness. Moreover, using a metallized film laminate reduces chemical compatibility problems that can arise between the metal and the polymeric substrate when metallizing articles in-situ.
To manufacture a metallized film laminate, a polymeric substrate is typically coated with a desired metal, often via vacuum deposition. Then, a polymeric clear coat is added to the metallization layer using conventional techniques, such as casting or doctor-blade applications. Using such metallized film laminates, though convenient, can result in an inferior finish as compared to that obtained by in-situ techniques. Therefore, it is desirable to achieve a finish similar to an in-situ process, yet with the convenience of a film laminate.
To that end, there are known to be metallized laminates that can be formed into desired shapes using conventional techniques. In addition, such formed laminates can be filled with thermoplastic polymer to produce a solid article having a similar bright finish as an article that has been metallized by in-situ methods.
For example, U.S. Pat. No. 4,101,698, for Elastomeric Reflective Metal Surfaces discloses a metallized elastomeric laminate that can provide a reflective metal surface finish for three-dimensional contoured shapes. In particular, the metallized layer is applied to an elastomeric film in separate, discontinuous planar segments. U.S. Pat. No. 4,115,619, for Highly Reflective Multilayer Metal/Polymer Composites discloses a bright multi-layer polymer composite formed by metallizing a thermoplastic polymer layer with a soft metal, such as indium. The metal layer is applied by conventional techniques, such as vacuum deposition, sputtering, or lamination. The metallized film can then be molded into a desired shape using conventional forming processes. U.S. Pat. No. 4,403,004, for a Sandwich Metalized Resin Laminate describes a metallized laminate formed of a thermoformable base layer that is coated on both sides with vapor deposited metal. This laminate is capable of being thermoformed to assume three-dimensional shapes.
Such formable film laminates have poor flexibility, however, often cracking when the metallized substrates are deformed. Moreover, such moldable films tend to lose luster over time. This is particularly pernicious with respect to metallized indium layers, which in the presence of halogen-containing polymers (e.g., polyvinyl chloride) can undergo an oxidation-reduction reaction that converts elemental indium to indium trichloride. Finally, to the extent such films are formed from continuous metallized layers, corrosion problems result.
Commonly-assigned U.S. application Ser. No. 09/268,085, filed Mar. 12, 1999, for a Bright Metallized Film Laminate discloses a metallized laminate having superior optical and deformation properties as compared to the prior art, and novel methods of making the same. In particular, U.S. application Ser. No. 09/268,085 discloses a bright metallized laminate including a discontinuous layer of indium islands deposited on a microscopically-smooth surface of a polyvinylidene difluoride-containing film. In this regard, the polyvinylidene difluoride-containing film preferably includes between about 30 percent and 90 percent by weight of polyvinylidene difluoride and between about 10 percent and 70 percent by weight of an acrylic polymer. U.S. application Ser. No. 09/268,085 is hereby incorporated by reference in its entirety.
Commonly-assigned, copending U.S. application Ser. No. 09/882,601, filed Jun. 15, 2001, for a Bright Indium-Metallized Formable Film Laminate, which is a continuation-in-part of U.S. application Ser. No. 09/268,085, also discloses a bright metallized formable film laminate having excellent optical and deformation properties. In particular, the bright metallized formable film laminate preferably includes a formable, weatherable clear coat film comprising polyvinylidene difluoride, a formable clear coat leveling layer on the weatherable clear coat film, and a discontinuous layer of indium islands deposited on the formable leveling layer, opposite the weatherable clear coat film. U.S. application Ser. No. 09/882,601 is hereby incorporated by reference in its entirety.
Finally, commonly-assigned, copending U.S. application Ser. No. 09/882,663, filed Jun. 15, 2001, for a Bright Tin-Metallized Formable Film Laminate, discloses a bright metallized formable film laminate having improved scratch resistance and adhesion, while retaining excellent optical and deformation properties. In particular, the bright metallized formable film laminate preferably includes a discontinuous layer of tin islands deposited on a microscopically-smooth surface of a formable, fluoropolymer clear coat film, preferably polyvinyl fluoride or polyvinylidene difluoride. U.S. application Ser. No. 09/882,663 is hereby incorporated by reference in its entirety.
While the metallized laminates disclosed by commonly-assigned and copending U.S. application Ser. Nos. 09/268,085, 09/882,601, and 09/882,663, offer significant improvement over the prior art, a need exists for alternative formable, bright metallized laminates that have possess superior optical and deformation properties.